Backlight assembly having LEDs and side reflectors and display apparatus having the same

ABSTRACT

A backlight assembly includes: a light emitting unit having a plurality of unit LEDs formed in a matrix, each of the unit LEDs having a red LED, a green LED, and a blue LED; a plurality of bottom reflectors disposed under the respective unit LEDs; and a plurality of side reflectors disposed around the respective unit LEDs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/586,373, filed Aug. 15, 2012, which is a continuation of U.S.application Ser. No. 11/720,239, filed May 25, 2007, now U.S. Pat. No.8,267,543, issued Sep. 18, 2012, which is the U.S. national stageapplication of International Patent Application No. PCT/KR2006/001868,filed May 18, 2006, which claims priority to Korean Patent ApplicationNo. 10-2005-0044369, filed May 26, 2005, all of which are incorporatedherein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a backlight assembly, and moreparticularly, to a backlight assembly and a display device having thesame.

BACKGROUND ART

In the fields of image display devices, cathode ray tubes (CRTs) arebeing replaced with liquid crystal display devices (LCDs) and plasmadisplay panels (PDPs).

LCDs are light and slim and have low power consumption. Also, LCDs donot radiate harmful electromagnetic waves. Because of these advantages,LCDs are considered as next-generation image display devices.

An LCD includes a bottom substrate, a top substrate, and a liquidcrystal layer. A plurality of thin film transistors (TFTs) are formed inthe bottom substrate, and color filters are arranged in the topsubstrate. The liquid crystal layer is interposed between the bottomsubstrate and the top substrate. The liquid crystal layer is formed byinjecting liquid crystal between the two substrates.

The TFTs formed in the bottom substrate function to transmit and controlelectric signals. Also, molecular structure of liquid crystal is changedaccording to voltage applied thereto and thus light transmissivity iscontrolled. Through these procedures, the controlled light passesthrough the top substrate and are displayed as a desired image.

Meanwhile, since the LCD is a light receiving device that displays animage by controlling an amount of incident light, the LCD requires abacklight assembly that is a light source emitting light on a liquidcrystal panel.

The backlight assembly is classified into a direct type backlightassembly and an edge type backlight assembly according to thearrangement of the light source. The direct type backlight assembly hashigh light utilization and is convenient to handle. Also, the directtype backlight assembly has no limitation in a screen size. Therefore,the direct type backlight assembly is widely used in large-sized LCDs.

External light sources for the backlight assembly can be appropriatelyselected according to size and purpose of the LCD. Examples of theexternal light sources include a point light source (e.g., anincandescent lamp, a white halogen lamp, etc.), a line light source(e.g., a hot cathode fluorescent lamp, a cold cathode fluorescent lamp,an external electrode fluorescent lamp, etc.), an electroluminescent(EL) lamp, and a surface light source (e.g. matrix type light emittingdiodes (LED)).

With the large scale of display devices, various researches areconducted to improve light efficiency of the backlight assembly forlarge-sized display devices, for example 30 inches or more.

DISCLOSURE OF INVENTION Technical Problem

The present invention is to provide a backlight assembly that canimprove the degree of color mixture and brightness uniformity, and adisplay device using the same.

Technical Solution

According to an aspect of the present invention, there is provided abacklight assembly including: a light emitting unit having a pluralityof unit LEDs formed in a matrix, each of the unit LEDs having a red LED,a green LED, and a blue LED; a plurality of bottom reflectors disposedunder the respective unit LEDs; and a plurality of side reflectorsdisposed around the respective unit LEDs.

In another aspect of the present invention, there is provided abacklight assembly including: a plurality of unit LEDs; a plurality ofbottom reflectors formed under the respective unit LEDs; a plurality ofside reflectors formed at boundaries of the respective unit LEDs; and adiffusion sheet supported by the side reflectors.

In a further another aspect of the present invention, there is provideda display device including: a backlight assembly having: a lightemitting unit including a plurality of unit LEDs formed in a matrix,each of the unit LEDs having a red LED, a green LED, and a blue LED; aplurality of bottom reflectors disposed under the respective unit LEDs;and a plurality of side reflectors disposed around the respective unitLEDs; and a panel receiving the light emitted from the backlightassembly.

Advantageous Effects

The backlight assembly and the image display device having the sameaccording to the present invention can improve the degree of colormixture and brightness uniformity when providing light for the imagedisplay. Also, the diffusion sheet can be easily installed and designed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a backlight assembly according to thepresent invention.

FIG. 2 is a plan view of an unit LED array in the backlight assemblyaccording to the present invention.

FIG. 3 is a perspective view of the unit LED array in the backlightassembly according to the present invention.

FIGS. 4 to 9 are plan views of unit LEDs in the backlight assemblyaccording to various embodiments of the present invention.

FIG. 10 is a sectional view illustrating an end portion of the sidereflector in the backlight assembly according to an embodiment of thepresent invention.

FIG. 11 is a sectional view illustrating an end portion of the sidereflector in the backlight assembly according to another embodiment ofthe present invention.

FIG. 12 is a sectional view illustrating an end portion of the sidereflector in the backlight assembly according to a further embodiment ofthe present invention.

FIG. 13 is a sectional view illustrating an end portion of the sidereflector in the backlight assembly according to a further embodiment ofthe present invention.

FIGS. 14 and 15 are plan views of the side reflectors in the backlightassembly according to embodiments of the present invention.

FIG. 16 is a perspective view of an embossed side reflector and anembossed bottom reflector in the backlight assembly according to afurther embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the embodiments of the present invention will be describedin detail with reference to the accompanying drawings.

FIG. 1 is a sectional view of a backlight assembly according to anembodiment of the present invention, and FIGS. 2 and 3 are a plan viewand a perspective view of a unit LED array in the backlight assembly ofFIG. 1, respectively.

Referring to FIGS. 1 to 3, the backlight assembly includes alight-emitting unit having a plurality of unit LEDs arranged in amatrix. Each of the unit LEDs has a red LED 15R, a green LED 15G, and ablue LED 15B.

Also, the backlight assembly includes a plurality of bottom reflectors11 disposed under the unit LEDs 15 and a plurality of side reflectors 13disposed around the unit LEDs 15.

As shown in FIGS. 1 to 3, the unit LED 15 may have a single red LED 15R,a single green LED 15G, and a single blue LED 15B.

As shown in FIGS. 4, 5, 7 and 9, the red LED, the green LED, or the blueLED can be provided in plurality.

Although not shown, each of the unit LEDs 15 may also have a pluralityof red LEDs, a plurality of green LEDs, and a plurality of blue LEDs.

The backlight assembly may further include a diffusion sheet 17 disposedon the light-emitting unit having the plurality of unit LEDs 15. Thus,the light emitted from the unit LEDs is incident on the diffusion sheet17.

The light reflected from the diffusion sheet 17 is again reflected fromthe side reflector 13 and the bottom reflector 11 and is again incidenton the diffusion sheet 17.

The side reflector 13 may be formed in one of a rectangular shape, acircular shape or an oval shape. Also, the side reflector 13 and thebottom reflector 11 may be formed in one body.

FIG. 2 is a plan view of the side reflector 13 of the rectangular shape.The side reflector 13 may also be pentagonal, hexagonal, and so on. FIG.14 is a plan view of the circular side reflector 23, and FIG. 15 is aplan view of the oval side reflector 33.

The side reflector 13 or the bottom reflector 11 may be coated fordiffusion and reflection.

A reflective surface of at the side reflector 13 and the bottomreflector 11 may be embossed. Also, a reflective surface of at the sidereflector 13 or the bottom reflector 11 may be embossed.

FIG. 16 is a perspective view of an embossed side reflector 43 and anembossed bottom reflector 41. Reference character 42 refers to a raisedprotuberance of the embossed side reflector 43 and embossed bottomreflector 41.

Light emitted upward from the unit LEDs 15 is white light. The whitelight is formed by the mixture of light emitted from the red LED 15R,the green LED 15G, and the blue LED 15B.

The backlight assembly of the present invention can have excellentcharacteristics of color mixture and brightness uniformity in the unitLEDs 15R, 15G and 15B. While the related art backlight assembly has onlyone reflector, the backlight assembly of the present invention has thebottom reflector 11 and the side reflectors 13 in each of the unit LEDs15.

That is, the unit LED 15 is surrounded by the bottom reflector 11 andthe side reflectors 13. The incident light on the reflectors is diffusedto have a plurality of orientation angles.

Thus, the mixture property and uniformity of the light emitted from theunit LEDs 15 can be improved and the reflectivity of the individuallight reflected from the unit LEDs 15 increased. Also, since light lossdoes not occur, the unit LEDs 15 can have high internal reflectionefficiency.

According to the embodiment of the preset invention, light of individualcolors from the LEDs 15R, 15G and 15B have an orientation angle largerthan 80 degrees. A primary light having a predetermined orientationangle is diffused to the diffusion sheet 17 and the side reflectors 13.

A secondary light reflected from the diffusion sheet 17 and sidereflectors 13 is diffused to the bottom reflector 11 and the sidereflectors 13. These diffused light change into tertiary and quaternarydiffused light at the bottom reflector 11 and the side reflectors 13 andare then incident on the diffusion sheet 17. Due to the diffused lighttraveling through these procedures, the light incident on the diffusionsheet 17 can have uniform color mixture and brightness.

FIGS. 4 to 9 are plan views of unit LEDs in the backlight assemblyaccording to various embodiments of the present invention.

The unit LED shown in FIG. 4 is a “1 in 1 square type” unit LED and hasLEDs arranged in a square shape.

The unit LED shown in FIG. 5 is a “1 in 1 line type” unit LED and hasLEDs arranged in a line shape.

The unit LED shown in FIG. 6 is a “3 in 1 chip on board type” unit LEDand has three LEDs molded in one body.

The unit LED shown in FIG. 7 is “4 in 1 chip on board type” unit LED andhas four LEDs molded in one body.

The unit LED shown in FIG. 8 is a “3 in 3 chip on board type” unit LEDand has three LEDs separately molded.

The unit LED shown in FIG. 9 is a “4 in 4 chip on board type” unit LEDand has four LEDs separately molded.

As shown in FIG. 4, each of the unit LEDs may have one red LED, twogreen LEDs, and one blue LED. Alternatively, as shown in FIG. 6, each ofthe unit LEDs may have one red LED, one green LED, and one blue LED.Also, as shown in FIG. 6, the LEDs may be molded in each unit LED.

Generally, the unit LEDs having the above-described structure emit lightupward. In some cases, the unit LEDs may be configured to emit lightlaterally by adding a lens on the unit LEDs. Since this structure iswell known, a detailed description thereof will be omitted.

FIGS. 10 to 13 are sectional views illustrating an end portion of theside reflector 13 in the backlight assembly according to embodiments ofthe present invention.

In the backlight assembly of the present invention, the diffusion sheet17 is supported on the side reflectors 13. Thus, the side reflectors 13can inhibit the diffusion sheet 17 from being bent downward.

That is, the backlight assembly of the present invention has anadvantage in that the diffusion sheet 17 provided on the light emittingunit is not bent due to the side reflectors 13. Therefore, a thicknessof the diffusion sheet 17 can be reduced.

In the backlight assembly shown in FIG. 10, the end portion of the sidereflection 13 is formed in a concave shape or a recessed shape.

In the backlight assembly shown in FIG. 11, the end portion of the sidereflection 13 is formed in a triangular shape.

In the backlight assembly shown in FIG. 12, the end portion of the sidereflection 13 is formed in a planar shape.

In the backlight assembly shown in FIG. 13, the end portion of the sidereflection 13 is formed in a semicircular shape or an oval shape.

In the side reflectors 13 of the backlight assemblies shown in FIGS. 10,11 and 12, a region where the light diffused from the adjacent unit LEDsare overlapped is formed above the diffusion sheet 17.

That is, a region where line extending along the inclined surfaces ofthe side reflectors 13 in the adjacent unit LEDs are met is formed abovethe diffusion sheet 17.

In the case of the backlight assembly shown in FIG. 11, a belt of whitecolor is formed by a boundary of the adjacent unit LEDs, that is, theoverlapping region 18 above the side reflector 13. On the contrary, inthe case of the backlight assemblies shown in FIGS. 10, 12 and 13, abelt of white color is not formed at a boundary of the adjacent unitLEDs, thus exhibiting uniform brightness.

As shown in FIGS. 10, 12 and 13, brightness uniformity of light emittedthrough the diffusion sheet 17 is improved.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present invention. Thus,it is intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

INDUSTRIAL APPLICABILITY

The backlight assembly and the image display device having the sameaccording to the present invention can improve the degree of colormixture and brightness uniformity when providing light for the imagedisplay. Also, the diffusion sheet can be easily installed and designed.

What is claimed is:
 1. A lighting unit comprising: a plurality of LEDunits; a supporter comprising a side portion providing a first recessand a bottom portion defining a second recess in which the plurality ofLED units is disposed; and a diffusion sheet supported by the sideportion of the supporter and covering the plurality of LED units,wherein the first recess provides a non-contacting portion with thediffusion sheet and is separated from the second recess in which theplurality of LED units is disposed, wherein the first recess is disposedunder the diffusion sheet, and wherein a bottom surface of the firstrecess is provided on the side portion of the supporter.
 2. The lightingunit according to claim 1, wherein the plurality of LED units has atleast two LEDs having wavelength different from each other.
 3. Thelighting unit according to claim 1, wherein the supporter is formed ofcircular shape.
 4. The lighting unit according to claim 1, wherein thefirst recess has a polygonal shaped cross section.
 5. The lighting unitaccording to claim 1, wherein the first recess is disposed within a topsurface of the side portion.
 6. The lighting unit according to claim 1,wherein the plurality of LED units is arranged in a square shape.
 7. Thelighting unit according to claim 1, wherein the plurality of LED unitsis arranged in a line shape.
 8. The lighting unit according to claim 1,wherein a top surface of the side portion has a contact portioncontacting directly with the diffusion sheet.
 9. A lighting unitcomprising: a plurality of LED units; a diffusion sheet covering theplurality of LED units; and a side supporter comprising a top surfacesupporting the diffusion sheet, a bottom surface surrounding theplurality of LED units, and a side portion between the top surface andthe bottom surface, wherein the top surface includes a first recessproviding a non-contacting portion with the diffusion sheet, wherein thefirst recess is disposed under the diffusion sheet, and wherein a bottomsurface of the first recess is provided on the side portion of thesupporter.
 10. The lighting unit according to claim 9, wherein thebottom surface of the side supporter defines a second recess in whichthe plurality of LED units is disposed.
 11. The lighting unit accordingto claim 10, wherein the first recess is separated from the secondrecess.
 12. The lighting unit according to claim 9, wherein theplurality of LED units has a plurality of LEDs.
 13. The lighting unitaccording to claim 12, wherein the plurality of LED units has at leasttwo LEDs having wavelength different from each other.
 14. The lightingunit according to claim 12, wherein the plurality of LED units isarranged in a square shape.
 15. The lighting unit according to claim 12,wherein the plurality of LED units is arranged in a line shape.
 16. Thelighting unit according to claim 12, wherein the top surface includes acontact portion contacting directly with the diffusion sheet.
 17. Thelighting unit according to claim 9, wherein the side supporter is formedof circular shape.
 18. A lighting unit comprising: a plurality of LEDunits; a diffusion sheet disposed on the plurality of LED units; asupporter comprising a contact portion contacting directly with thediffusion sheet, a first recess providing a non-contacting portion withthe diffusion sheet, a bottom portion defining a second recess in whicheach of the plurality of LED units is disposed, and a side portionbetween the contact portion and the bottom portion, wherein the firstrecess is disposed under the diffusion sheet, and wherein a bottomsurface of the first recess is provided on the side portion of thesupporter.
 19. The lighting unit according to claim 18, wherein thefirst recess is disposed within a top surface of the side portion. 20.The lighting unit according to claim 18, wherein the supporter is formedof circular shape.